Nervous system disorders, including neurological, disorders, affect millions of people, causing death and a degradation of life. Nervous system disorders include disorders of the central nervous system, peripheral nervous system, and mental health and psychiatric disorders. Such disorders include, for example without limitation, epilepsy, Parkinson's disease, essential tremor, dystonia, and multiple sclerosis (MS). Additionally, nervous system disorders include mental health disorders and psychiatric disorders which also affect millions of individuals and include, but are not limited to, anxiety (such as general anxiety disorder, panic disorder, phobias, post traumatic stress disorder (PTSD), and obsessive compulsive disorder (OCD)), mood disorders (such as major depression, bipolar depression, and dysthymic disorder), sleep disorders (narcolepsy), obesity, and anorexia. As an example, epilepsy is the most prevalent serious neurological disease across all ages. Epilepsy is a group of neurological conditions in which a person has or is predisposed to recurrent seizures. A seizure is a clinical manifestation resulting from excessive, hypersynchronous, abnormal electrical or neuronal activity in the brain. (A neurological event is an activity that is indicative of a nervous system disorder. A seizure is a type of a neurological event.) This electrical excitability of the brain may be likened to an intermittent electrical overload that manifests with sudden, recurrent, and transient changes of mental function, sensations, perceptions, and/or involuntary body movement. Because the seizures are unpredictable, epilepsy affects a person's employability, psychosocial life, and ability to operate vehicles or power equipment. It is a disorder that occurs in all age groups, socioeconomic classes, cultures, and countries. In developed countries, the age-adjusted incidence of recurrent unprovoked seizures ranges from 24/100,000 to 53/100,000 person-years and may be even higher in developing countries. In developed countries, age specific incidence is highest during the first few months of life and again after age 70. The age-adjusted prevalence of epilepsy is 5 to 8 per 1,000 (0.5% to 0.8%) in countries where statistics are available. In the United States alone, epilepsy and seizures affect 2.3 million Americans, with approximately 181,000 new cases occurring each year. It is estimated that 10% of Americans will experience a seizure in their lifetimes, and 3% will develop epilepsy by age 75.
There are various approaches in treating nervous system disorders. Treatment therapies can include any number of possible modalities alone or in combination including, for example, electrical stimulation, magnetic stimulation, drug infusion, and/or brain temperature control.
Several devices have been disclosed for the treatment of a neurological disorder. Examples of such devices include U.S. Pat. No. 5,832,932, Elsberry, Method of Treating Movement Disorders By Brain Infusion, which discloses techniques and apparatus for infusing drugs into the brain to treat movement disorders resulting in abnormal motor behavior. An implantable pump and a catheter, the catheter having a proximal end coupled to the pump and a discharge portion for placement adjacent a predetermined infusion site in the brain for infusing therapeutic dosages of the one or more drugs into the brain. The pump is operated to discharge a predetermined dosage of the one or more drugs through the discharge portion of the catheter into the infusion site. A sensor may be used in combination with the implantable pump and catheter, whereby the sensor generates a signal relating to the extent of the abnormal motor behavior. The therapeutic dosage is regulated so that the dosage is adjusted in response to an increase in the abnormal behavior to decrease the abnormal motor behavior.
U.S. Pat. No. 6,591,138, Fischell, Low Frequency Neurostimulator For the Treatment of Neurological Disorders, discloses a system for treating neurological conditions by low frequency time varying electrical stimulation includes an electrical device for applying such low-frequency energy, in a range below approximately 10 Hertz, to the patient's brain tissue. An implantable embodiment applies direct electrical stimulation to electrodes implanted in or on the patient's brain, while a non-invasive embodiment causes a magnetic field to induce electrical currents in the patient's brain.
U.S. Pat. No. 6,609,030, Rezai, Method of Treating Psychiatric Diseases By Neruomodulation Within the Dorsomedial Thalamus, discloses a method for treating psychiatric diseases such as Affective Disorder (including Major Depression and Bipolar Disorder), Anxiety Disorder (including General Anxiety Disorder, Obsessive Compulsive Disorder and Panic Disorder) by stimulation (either electrical and/or chemical) of the thalamus, and in particular a region within the dorsomedial nucleus of the thalamus. The method includes the steps of determining a common group of patients, each suffering from a common specific diagnosis or a psychological disorder; determining which common region of the patients' thalami are involved in carrying the pathological electrical signals and/or metabolic activity which may otherwise be generated in dissimilar and disparate regions of the brains of the patients; surgically implanting an electrode and/or catheter and electrical signal generating device and/or drug pump such that the electrode and/or catheter is positioned within the region of the thalamus identified as the dorsomedial nucleus; and selectively adjusting the level of electrical and/or chemical stimulation in accordance with the specific effect of the stimulation of the patient. In particular, the region of the thalamus most frequently associated with the aforementioned psychiatric disease is the dorsomedial nucleus.
U.S. Published Patent Application No. 2004/0002635, Hargrove, Method and Apparatus For Utilizing Amplitude-Modulated Pulse-Width Modulation Signals For Neurostimulation and Treatment of Neurological Disorders Using Electrical Stimulation, discloses a computing device-controlled system is described for the generation of amplitude-modulated pulse-width modulation (AMPWM) signals for use in treating neurological dysfunction via cranial neurostimulation, where the AMPWM signal is specifically designed to minimize the electrical impedance of the tissues of the head. A low-frequency carrier signal is determined for the AMPWM signal by measuring EEG activity at a reference site or sites, generally corresponding with the location of suspected brain dysfunction. Carrier signal frequency is variably related to critical frequency components of the EEG power spectral density, determined from statistical analysis of amplitudes and variability, and dynamically changed as a function of time to prevent entertainment. The AMPWM signal is presented to a subject via a plurality of neurostimulation delivery modes for therapeutic use.
Devices and methods have also been developed to sense a condition and then respond with a treatment for a certain neurological disorder. For example, U.S. Pat. No. 6,647,296, Fischell et al, Implantable Apparatus For Treating Neurological Disorders, discloses a multiple electrode, closed-loop, responsive system for the treatment of certain neurological diseases such as epilepsy, migraine headaches and Parkinson's disease. Brain electrodes would be placed in close proximity to the brain or deep within brain tissue. When a neurological event such as the onset of an epileptic seizure occurs, EEG signals from the electrodes are processed by signal conditioning means in a control module that can be placed beneath the patient's scalp, within the patient's scalp, or situated externally on the patient. Neurological event detection means in the control module will then cause a response to be generated for stopping the neurological event. The response could be an electrical signal to brain electrodes or to electrodes located remotely in the patient's body. The response could also be the release of medication or the application of a sensory input such as sound, light or mechanical vibration or electrical stimulation of the skin. The response to the neurological event can originate from devices either internal or external to the patient. The system also has the capability for multi-channel recording of EEG related signals that occur both before and after the detection of a neurological event. Programmability of many different operating parameters of the system by means of external equipment provides adaptability for treating patients who manifest different symptoms and who respond differently to the response generated by the system.
Examples in the cardiac field include U.S. Pat. No. 6,731,984, Cho et al, Method For Providing A Therapy To a Patient Involving Modifying the Therapy After Detecting an Onset of Sleep in the Patient and Implantable Medical Device Embodying Same; U.S. Pat. No. 5,284,491, Sutton et al, Cardiac Pacemaker With Hysteresis Behavior; and U.S. Pat. No. 5,193,535, Bardy et al, Method and Apparatus For Discrimination of Ventricular Tachycardia From Ventricular Fibrillation and For Treatment Thereof.
Cho et al '984 discloses an implantable medical device system is described including an implantable medical device for implantation in a patient. One embodiment of the implantable medical device includes a therapy component for providing a therapy to the patient, a minute ventilation (MV) sensing circuit producing MV values indicative of a MV of the patient at time intervals, and computational circuitry. The computational circuitry receives a number of the MV values over a period of time, calculates a statistical parameter (e.g., a mean) of the MV values, and calculates a deviation of the MV values from the statistical parameter (e.g., a standard deviation of the MV values). The computational circuitry detects an onset of sleep in the patient when the deviation of the MV values from the statistical parameter is less than a predetermined MV threshold value, and signals the therapy component to modify the therapy when the onset of sleep is detected in the patient. A method is disclosed for providing therapy to a patient, including detecting an onset of sleep in the patient, and modifying the therapy following the detecting the onset of sleep in the patient.
Sutton et al '491 discloses a pacemaker having a hysteresis feature which permits intrinsic heart activity, controlled by the sinus node to resume optimally after pacing. The pacemaker has a programmable lower rate and upper rate, a programmable lower hysteresis rate (LRH) corresponding to a lower rate hysteresis interval (LRHI), and a programmable rate (IR) intermediate an upper pacing rate (UR) and a lower pacing rate (LR). A microprocessor measures the average rate of change MAVG in the intervals between consecutive ventricular depolarizations, and compares the last intrinsic escape interval RRN to the lower rate hysteresis interval (LRHI). If the last intrinsic escape interval RRN is longer than the lower rate hysteresis interval (LRHI), and if the value of MAVG is greater than a first preselected value SLI but less than a second preselected value SL2, the pacemaker stimulates at the lower rate hysteresis (LRH) and thereafter gradually increases the pacing rate up to the intermediate rate (IR). A time counter maintains a continuous pacing at the intermediate rate (IR) for a predefined period of time, and the pacing rate is gradually decreased toward the lower pacing rate (LR).
Bardy et al '535 discloses an implantable cardioverter/defibrillator provided with method and apparatus for discrimination between ventricular tachycardia and ventricular fibrillation. The device is provided with two pairs of electrodes, each pair of electrodes coupled to processing circuitry for identifying a predetermined fiducal point in the electrical signal associated with a ventricular depolarization. The cumulative beat to beat variability of the intervals separating the two identified fiducal points, over a series of detected depolarizations is analyzed. The result of this analysis is used to distinguish between ventricular tachycardia and ventricular fibrillation.
Devices and methods have also been developed that provide multiple treatments for a single disorder. An example is U.S. Pat. No. 6,094,598, Elsberry, Method of Treating Movement Disorders By Brain Stimulation and Drug Infusion, which discloses techniques using one or more drugs and electrical stimulation for treating neural disorders, including movement disorders resulting in abnormal motor response, by means of an implantable signal generator and electrode and an implantable pump and catheter. A sensor is used to detect activity resulting from the neural disorder. A microprocessor algorithm analyzes the output from the sensor in order to regulate the stimulation and drug dosage delivered to the neural tissue.
Also, U.S. Pat. No. 5,713,923, Ward et al, Techniques For Treating Epilepsy By Brain Stimulation and Drug Infusion, U.S. Pat. No. 5,578,702, Ward et al, Techniques For Treating Epilepsy By Brain Stimulation and Drug Infusion, disclose techniques using one or more drugs and electrical stimulation for treating a neurological disorder, including epilepsy, by means of an implantable signal generator and electrode and an implantable pump and catheter. A sensor is used to detect a seizure or symptoms resulting from the onset of a seizure. A microprocessor algorithm analyzes the output from the sensor in order to regulate the stimulation and drug dosage delivered to the neural tissue.
U.S. Pat. No. 6,176,242, Rise, Method of Treating Manic Depression By Brain Infusion, discloses techniques using one or more drugs, electrical stimulation or both to treat depression or manic depression by means of an implantable signal generator and electrode and/or an implantable pump and catheter. A catheter is surgically implanted in selected sites in the brain to infuse the drugs, and one or more electrodes are surgically implanted in the brain at selected sites to provide electrical stimulation.
U.S. Published Patent Application No. US2004/0138517 (A1), Osorio et al, Multi-Modal Operation of a Medical Device System, discloses multi-modal operation for the treatment of a nervous system disorder. The medical device system supports both a first feature and a second feature associated with treatment therapy with an implanted component and an external component and may support a plurality of features during a treatment interval.